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<div id="printheader"><h1 class="p_Heading1" style="page-break-after: avoid;"><span class="f_Heading1">最后手段字体</span></h1>
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     <p class="crumbs"><b>导航：</b>&nbsp;编辑字体 &gt; 编辑字体 &gt;</p>
     <h1 class="p_Heading1" style="page-break-after: avoid;"><span class="f_Heading1">最后手段字体</span></h1>
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<p class="p_Normal">当操作系统（或自带文本渲染的软件）需要显示文本时，它必须判定所选字体中的字符是否可用。如果缺少某个字符，它会使用应急替代机制，例如它将在其他字体中查找该字符。<b>最后手段（Last Resort）字体</b>可确保至少有一种字体能够显示这等缺失的字符，这些字体也称为<span style="font-weight:bold;">后备字体</span>。</p>
<h2 class="p_Heading2" style="page-break-after: avoid;"><span class="f_Heading2">字符到字形索引的映射</span></h2>
<p class="p_Normal">通常，最后手段字体包含一个用于特定字符组的字形，该字形代表特定的字符范围。这将确保字形的数量保持在较低水平，同时字体可以包含对所有 Unicode 平面的映射，涵盖超过一百万个代码点。在 OpenType 规范中，基本上有两种格式，可以存储许多字符到字形索引的映射。一般格式对于常规字体来说非常有效，而压缩(compact)格式对字符范围映射到单个字形的存储进行了优化。</p>
<p class="p_Normal">Windows 不支持使用压缩格式的最后手段字体。Apple 的最后手段字体使用压缩格式。它预装在 Mac 上并包含所有 Unicode 字符。最后手段字体的文件大小为 3KB，但如果以一般格式保存，它将变为 12.7 MB 。</p>
<p class="p_Normal">默认情况下，FontCreator 以一般格式保存字体，除非您设置了<a href="fontheaderflags.html" class="topiclink">最后字体头标志</a>。</p>
<h2 class="p_Heading2" style="page-break-after: avoid;"><span class="f_Heading2">空白字体</span></h2>
<p class="p_Normal">一些网站使用空白（Blank）字体，来检测访问者的系统上是否存在某款字体。其他网站使用这种字体，来确保不显示其他字体的字符。</p>
<p class="p_Normal">&nbsp;</p>
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